reverse polarity electrolytic caps

Discussion in 'General Electronics Chat' started by richbrune, Jan 30, 2009.

  1. richbrune

    Thread Starter Senior Member

    Oct 28, 2005
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    The attached drawing has V3 as a 12volt to 0 volt square wave. I'll try to post the netlist.
    I'd like to know if this is a bad idea, and if there's a problem with the polarity of the 4.7 uf cap
    Thanks, Richard Brune
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    1,728
    If you put a reverse polarity charge across a polarized electrolytic capacitor, you will most likely destroy it in very short order.

    You can get non-polarized electrolytic capacitors.

    You could also use two 10uF polarized caps back-to-back.

    Or better, you could use a poly cap that is not polarized. Poly caps have lower leakage than electrolytics, along with very good frequency response.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    The easy way out is to obtain a bipolar capacitor, or else to use two 10 uF electrolytics in series with two terminals of the same polarity in common.
     
  4. richbrune

    Thread Starter Senior Member

    Oct 28, 2005
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    So I am getting reverse polarity form this circuit?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Have you run the simulation on it? At least the DC analysis part?
     
  6. richbrune

    Thread Starter Senior Member

    Oct 28, 2005
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    Test Point V2 goes from 10volts to 0 volts, but I'm not good enough with these things to tell if the polarity at C2 is reversed
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    I was wondering about that the other day, won't one or the other be distroyed?
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    Nope, it's a strange thing about back-to-back electrolytics. Hook 'em up with both + or - terminals connected, and they act like a non polar capacitor.
     
  9. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    One also gets the bonus of doubling the working voltage. (Put high value resistors in parallel with the caps if taking advantage of this.)

    Of course, one halves the capacitance.
     
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